The present invention relates to a inspection technique of comparing an inspection image of an object to be inspected obtained by using light, electron beam, or the like and a reference image corresponding thereto and of detecting a defect such as a fine pattern defect or a foreign material occurring on a substrate from a difference between the images and, in particular, to a technique effectively applied to a defect inspection system for performing appearance inspection of a substrate for a semiconductor wafer, a photomask, a liquid crystal, or the like.
For example, in a defect inspection apparatus constituting the defect inspection system, a plurality of inspection condition items are present and the number of combinations thereof is tens or more. Therefore, prior to inspection, work (condition selecting work) is required for performing an inspection on some inspection conditions and selecting one condition that has the highest sensitivity of defect detection from the inspected conditions. However, there is such a problem that considerable skill is required to the work because of taking some of trial and error and further heavy workload is required.
As a method for solving the above problem, for example, techniques disclosed in Japanese Patent Laid-open Publication No. 2002-303586 and Japanese Patent No. 3300830 are known. The technique disclosed in Japanese Patent Laid-open Publication No. 2002-303586 allows even an unskilled person to set an inspection condition having high sensitivity of defect detection easily and in a short period of time by: inspecting an object to be inspected on a plurality of test conditions constituted from a plurality of inspection condition items set in advance while automatically changing inspection conditions; quantitatively arranging and displaying images, contrasts, luminance distributions, and the like on respective test conditions; performing automatic defect/misinformation discrimination based on the test inspection result; displaying the classification result on a map, and selecting the condition having a low misinformation ratio.
The technique disclosed in Japanese Patent No. 3300830 provides a method of comparing information about a defect detected on a defect inspection apparatus with data extracted from distribution of scattering light from a defect obtained according to simulation to classify the detected defects according to sizes and shapes, thereby making it possible to detect presence or absence of a defect such as a foreign material on a substrate, on a surface of which a pattern is formed, and further detect the size or shape of the defect rapidly and easily if the defect is present.
However, in the technique disclosed in Japanese Patent Laid-open Publication No. 2002-303586, a whole wafer is inspected while changing the inspection conditions and defect maps are arranged and displayed for the respective conditions, so that it is necessary to inspect the entire wafer by the number of inspection conditions. For example, when the technique is applied to an inspection apparatus whose throughput is not high, there is such a problem that an unrealistically long prior evaluation time is necessary. In addition, a sample that is an object to be inspected is required for setting an inspection condition.
Also, the technique disclosed in Japanese Patent No. 3300830 provides a method for classifying the simulation results according to the sizes and shapes of the defects. The method is useful for classifying the defects, but does not assist in setting of the inspection condition.